1. Field
Embodiments of the present invention relate to a valve structure of a shock absorber which forms flow channels in two directions of working fluid passing through the valve structure so as to slow change of damping force when the moving velocity of a piston is changed between a low velocity and a middle and high velocity and forms one of the two flow channels as a variable flow channel to improve ride comfort of a vehicle.
2. Description of the Related Art
In general, a damping device damping impact or vibration applied to an axle from the road surface during driving to improve ride comfort is installed in a vehicle, and a shock absorber is used as one such damping device.
The shock absorber is operated according to vibration of the vehicle corresponding to the state of the road surface, and damping force generated from the shock absorber is varied according to operating velocity of the shock absorber, i.e., according to whether or not the operating velocity of the shock absorber is high or low.
Ride comfort and driving stability of the vehicle may be controlled by adjustment of damping characteristics generated from the shock absorber. Therefore, when the vehicle is designed, adjustment of damping force of the shock absorber is important.
A conventional piston valve is designed to have regular damping characteristics at a high velocity, a middle velocity and a low velocity using a single flow channel, and thus, if damping force at the low velocity is lowered to facilitate improvement of ride comfort, damping force at the high and middle velocities may be lowered.
Further, the conventional shock absorber has characteristics in which damping force is exponentially increased at a low velocity and is linearly changed at a middle and high velocity according to flow velocity of the working fluid passing through the single flow channel (i.e., moving velocity of the piston valve), and since a damping force curve is rapidly changed at an inflection point from the low velocity to the middle and high velocity, ride comfort of a vehicle may be lowered.